001/*
002 * Copyright 2021-2024 Ping Identity Corporation
003 * All Rights Reserved.
004 */
005/*
006 * Copyright 2021-2024 Ping Identity Corporation
007 *
008 * Licensed under the Apache License, Version 2.0 (the "License");
009 * you may not use this file except in compliance with the License.
010 * You may obtain a copy of the License at
011 *
012 *    http://www.apache.org/licenses/LICENSE-2.0
013 *
014 * Unless required by applicable law or agreed to in writing, software
015 * distributed under the License is distributed on an "AS IS" BASIS,
016 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
017 * See the License for the specific language governing permissions and
018 * limitations under the License.
019 */
020/*
021 * Copyright (C) 2021-2024 Ping Identity Corporation
022 *
023 * This program is free software; you can redistribute it and/or modify
024 * it under the terms of the GNU General Public License (GPLv2 only)
025 * or the terms of the GNU Lesser General Public License (LGPLv2.1 only)
026 * as published by the Free Software Foundation.
027 *
028 * This program is distributed in the hope that it will be useful,
029 * but WITHOUT ANY WARRANTY; without even the implied warranty of
030 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
031 * GNU General Public License for more details.
032 *
033 * You should have received a copy of the GNU General Public License
034 * along with this program; if not, see <http://www.gnu.org/licenses>.
035 */
036package com.unboundid.util;
037
038
039
040import java.security.SecureRandom;
041
042
043
044/**
045 * This class provides a means of obtaining a thread-local {@code SecureRandom}
046 * instance that can be used without synchronization or contention.
047 */
048@ThreadSafety(level=ThreadSafetyLevel.COMPLETELY_THREADSAFE)
049public final class ThreadLocalSecureRandom
050{
051  /**
052   * The thread-local instances that have been created.
053   */
054  @NotNull private static final ThreadLocal<SecureRandom> INSTANCES =
055       new ThreadLocal<>();
056
057
058
059  /**
060   * Prevents this utility class from being instantiated.
061   */
062  private ThreadLocalSecureRandom()
063  {
064    // No implementation is required.
065  }
066
067
068
069  /**
070   * Retrieves a thread-local {@code SecureRandom} instance.
071   *
072   * @return  A thread-local {@code SecureRandom} instance.
073   */
074  @NotNull()
075  public static SecureRandom get()
076  {
077    SecureRandom random = INSTANCES.get();
078    if (random == null)
079    {
080      random = CryptoHelper.getSecureRandom();
081      INSTANCES.set(random);
082    }
083
084    return random;
085  }
086}